最新刊期
卷 ， 期 9 ， 2016
- 摘要：Poly(amino acid) is an important biomimetic material due to its unique biocompatibility and potential application in gene transfection, drug delivery, and prevention of viral infections.For example, ε-poly-lysine (ε-PL) is an uncommon cationic homopolymer produced by the fermentation process.Due to its significant antimicrobial activity and nontoxicity to humans, ε-PL is now industrially produced as an additive in food and cosmetics, biodegradable fibers, highly water absorbable hydrogels and drug carriers.However, due to the lack of appropriate polymerization method, ε-PL is now produced mainly by a fermentation process.The ε-PL with a molecular weight less than 4×103 is obtained by biosynthetic method and no copolymers composed of lysine and other amino acids can be found in the producer strains, probably because the two amino acids are polymerized by different enzymes.Consequently, the composition and properties of the resultant polymers are hard to regulate.Here, we report a new chemical strategy, based on ring-opening polymerization (ROP) of lactam, to obtain ε-PL with diverse molecular weight from renewable lysine monomer.Compared with ROP of lysine via the N-carboxyanhydride (NCA) intermediate, this new strategy for ε-PL, through ROP and without phosgene, allows for new opportunities in biomaterials applications.Moreover, this methodology may provide access to the production of γ-polyglutamate and β-poly(aspartic acid) from glutamic acid and aspartic acid monomers, respectively.关键词：Poly(amino acid);ε-Poly-lysine;Lactam;Ring-opening polymerization;N-Carboxyanhydride
- 162
- |
- 48
- |
- 17
发布时间：2021-03-19 - 摘要：Biomacromolecules are the foundation of life.In the natural environment (aqueous solution), the biomacromolecules exist in the precise supramolecular structures.To date, many kinds of water soluble polymers have been synthesized.However, few of them can be self-assembled into precise supramolecular structures in aqueous solution.Compared to synthetic polymers, biomacromolecules are special and magic.Recently, the author's group utilized single-molecule force spectroscopy (SMFS) to study the interactions between biomacromolecules and water.For ssDNA, there is an evident deviation between the single-chain force-extension (F-E) curves obtained respectively in the aqueous solution and nonpolar solvent, which is estimated to be 0.58kBT per base in energy.Comparing to synthetic water soluble polymers, this energy is rather low.The weak competition influence of water may be a precondition for a stable dsDNA to exist in water.For dsDNA, the double-helix structure will be unwound when it is dragged across the water/nonpolar solvent interface.For a polyprotein (polyI27), the unfolding of the globules in water can be observed as saw-tooth F-E curve.However, the same sample in nonpolar solvent only presents an pure elastic behaviour similar to that of polypeptide.Similarly, a clear deviation can also be observed when comparing the single-molecule F-E curves of other biomacromolecules (such as RNA and natural cellulose) obtained respectively in the aqueous solution and nonpolar solvent.It was shown that in nonpolar solvents, the supramolecular structures of biomacromolecules will be unstable, resulting in the denaturation of the biomacromolecules.Water is the switch that regulates the supramolecular structures and functions of biomacromolecules.The concept of aqueous environment adaptability is proposed.It is speculated that biomacromolecules were selected by the aqueous environment during the early chemical evolution.The aqueous environment adaptability may be one important division between the non-biological macromolecules and the biological ones.It is anticipated that more secret of life will be unveiled with further investigation on water and biomacromolecules.关键词：Atomic force microscopy;Single-molecule force spectroscopy;Biomacromolecules;Aqueous environment;Chemical evolution
- 41
- |
- 14
- |
- 3
发布时间：2021-03-19 - 摘要：Selective transformation of CO2 into degradable polycarbonates by the alternating copolymerization with epoxides represents an important green polymerization process.Although the commercialization of CO2 copolymers (CO2-based polycarbonates) has already made a certain progress in recent years, the further development of this green technology is suffering from material performance as well as product type etc.The main problem is that all the previously reported CO2 copolymers are amorphous and have low glass transition temperatures, which make the strength sharply decrease at high temperatures.This paper focuses on the recent progress of the stereospecific copolymerization of CO2 and epoxides, including design of highly stereoregular catalysts based on mononuclear and dinuclear cobalt(Ⅲ) complexes, and discovery of various crystalline CO\-2-based polycarbonates.Although various highly isotactic CO2 copolymers from terminal epoxides were prepared, only two of them were found to be crystallized.On the contrary, most highly isotactic CO2 copolymers from meso-epoxides are typical semi-crystalline materials, possessing the melting points of 179-257℃, dependent on the employed meso-epoxides. Notably, various crystalline stereocomplexes were found to be formed in the blend of equivalent crystalline or amorphous isotactic (R)-and (S)-polycarbonates.They show the enhanced thermal stability and new crystalline behavior, significantly distinct from the component enantiomer.Moreover, the cocrystallization of amorphous isotactic polycarbonates with different chemical structures and opposite configurations provided novel crystalline hetero-stereocomplexed polymeric materials.Furthermore, racemic bimetallic cobalt catalyst system mediated stereoselective copolymerization of CO2 and meso-epoxides afforded novel intramolecular stereocomplexed polycarbonates, due to highly enantioselective chain growth in an enantiopure catalyst molecule and the copolymer-chain transfer between different configuration catalyst molecules resulting in the formation of the isotactic multiblock polycarbonates.关键词：Carbon dioxide;Epoxide;Stereoregularity;Asymmetric polymerization;Crystallination;Stereocomplex
- 134
- |
- 33
- |
- 10
发布时间：2021-03-19
Feature Articles
- 摘要：In recent years, fast-scan chip-calorimeter (FSC), as a new development from conventional differential scanning calorimeter (DSC), has gave an impetus to the progress in the field of polymer crystallization and melting.As the first user in this field of China, we made a survey on the recent progress of the issue.We first introduced the history of commercial FSC, followed with its measurement techniques on polymer semi-crystalline samples.We then provided several examples on the applications of this technique in the study of polymer crystallization and melting behaviors, including overall crystallization kinetics, crystal nucleation kinetics, the effects of nucleation agents, fillers and comonomers on crystallization, the identification of multiple melting peaks, the irreversible and reversible melting of chain-folded lamellar crystals, and the melting of macromolecules with strong intermolecular interactions.The great expansion of temperature-scanning rates in Flash DSC could match to either industrial processing or molecular simulation, and thus provide rich information of combinational approaches on polymer crystallization, annealing and melting behaviors for our better understanding.We hope that this survey can help the readers on reading the literatures related to FSC or on considering this technique as a useful tool in solving the problems related to polymer crystallization and melting, or similar behaviors of other materials.关键词：Thermal analysis;Polymer physical properties;Crystallization
- 166
- |
- 54
- |
- 5
发布时间：2021-03-19
Reviews
- 摘要：Nonwoven fabric reinforced poly(vinylidene fluoride) (PVDF)/graphene(GE) oil-absorptive composite membrane (NR-PGM) was prepared by a coating method.NR-PGM consisted of PVDF/GE separation layer and polyethylene terephthalate-polyamide nonwoven fabric matrix layer.Nonwoven fabric was pretreated by NaOH solution for better interface bonding, and PVDF/GE separation layer was obtained by non-solvent induced phase separation (NIPS) method with PVDF as the polymer matrix, hydrophobic SiO2 and GE as additives, dioctyl phthalate (DOP) as the pore-forming agent, and dimethylacetamide (DMAc) as the solvent.Membrane characterization was conducted through SEM, water contact angle and oil contact angle, pore diameter distribution, mechanical strength, water entry pressure, oil flux and flux recovery rate.The results indicated that the NR-PGM exhibited hydrophobicity and superoleophilicity.SEM images indicated that the dense microvoids were uniformly distributed on the top surface of separation layer, and the cross section of separation layer had an asymmetrical structure that consisted of finger-like pore structures on the top and sponge-like pore structures on the buttom.Moreover, the average pore diameter was about 340 nm, water contact angle was up to 95.4° and oil contact angle was nearly 0°, water entery pressure was up to 0.14 MPa, and the kerosene and diesel oil flux reached 118.22 and 218.25 L/m2h.NR-PGM was competent for continuous oil/water separation through vacuum pressure.At first, the oil/water separation efficiency was nearly 97%.After being used for 10 times, the oil/water separation efficiency remained about 95%.关键词：Polyvinylidene fluoride;Graphene;Hydrophobicity and superoleophilicity;Continuous oil/water separation
- 25
- |
- 17
- |
- 3
发布时间：2021-03-19 - 摘要：The chain relaxation behavior of ethylene-propylene-diene rubber (EPDM) was investigated by dynamic mechanical analysis (DMA).The results indicated that there were three tanδ peaks for EPDM at low frequencies, which were attributed to glass transition (α transition), sub-Rouse mode (α' transition) and Rouse mode (α" transition), respectively.In addition, compared with the glass transiton, sub-Rouse mode has a much stronger frequency-dependence, showing that the sub-Rouse mode moves to high temperature faster than the α mode with the augment of frequency, which is sensible and consistent with the previous works as the local segmental motions are more intermolecularly coupled than the sub-Rouse mode relaxation in polymers, such as PS, PVAc and PMMA.After comprehensive analyses of frequency-domain spectra of EPDM via figuring out the temperature dependence of relaxation time, relaxation strength, coupling parameter and shape parameter, a dynamic crossover at TB-384 K was found in sub-Rouse (α') mode.What's more, the crossover relaxation time τα'(TB) is calculated as 0.11 s, approximately, which is remarkably close to that of PS, PVAc and PVAc/PEO blends (10(-0.5±0.5) s), indicating that this crossover arises at a particular point of relaxation time.According to the coupling model, the crossover is suggested to be caused by the strong increase of intermolecular cooperativity below TB.关键词：EPDM;Relaxation time;Coupling model;Intermolecular cooperativity
- 15
- |
- 11
- |
- 1
发布时间：2021-03-19 - 摘要：A facile approach for preparing core-shell composite microspheres with tunable surface coverage was proposed.High performance liquid chromatography and zeta potential results showed that, rebalancing of emulsifiers' adsorption and desorption occurred when core and shell particles were mixed, and the cationic emulsifier desorbed from the core particle might neutralize the anionic emulsifier on the surface of shell particles.This resulted in a low gap of the zeta potential values between the core and the shell particles, and led to fail of the electrostatic-induced heterocoagulation.It was found that both the stability of the dispersion system and the contents of the free cationic emulsifier could be regulated by adding nonionic emulsifier.Subsequently, the heterocoagulation was successfully achieved as the contents of total emulsifier were kept at 1 wt%.Thus, by adjusting the ratio of nonionic and cationic emulsifier content, the surface coverage of composite microspheres could be easily controlled.The influence of pH value and electrolyte content on the surface coverage of core-shell composite microspheres was also discussed in this work.关键词：Core-shell composite microspheres;Heterocoagulation;Emulsifier adsorption;Tunable surface coverage
- 26
- |
- 13
- |
- 0
发布时间：2021-03-19 - 摘要：Acrylate-terminated PLA-PEG-PLA macromer (PELA-DA) and β-cyclodextrin polymer modified with glycidyl methacrylate (CDP-g-GMA) were synthesized, and copolymer films with different compositions were prepared via UV-initiated free radical polymerization of PELA-DA, CDP-g-GMA and N-vinylpyrrolidone (VP) in DMF.The 1H-NMR analysis confirmed the successful synthesis of PELA-DA and CDP-g-GMA macromers.The structure and properties of the copolymer films were characterized by X-ray diffraction (XRD), dynamic thermomechanical analysis (DTMA), thermal gravity analysis (TGA), water uptake and in vitro degradation.XRD exhibited that the crystallinity of PELA-DA and CDP-g-GMA components was suppressed and disturbed in the copolymer films.The water uptake and in vitro degradation measurements showed that the hydrophilicity and hydrolytic degradation of the copolymer films were improved due to the introduction of CDP-g-GMA macromer.DTMA and TGA results displayed that storage modulus (E'), glass transition temperature (Tg) and thermal stability of the resultant copolymer films increased as the contents of β-cyclodextrin polymer macromer incorporated increased.In addition, using methyl orange (MO) as a water-soluble model drug, the MO loading and release profiles of the copolymer films were evaluated.It was found that the MO loading amounts of the films increased with the increase of incorporated CDP-g-GMA content.After a burst release of 12 h at the first stage, the MO release profile was in a slow and sustained manner.关键词：Macromer;Cyclodextrin;Copolymer film;Degradability;Drug release
- 27
- |
- 14
- |
- 0
发布时间：2021-03-19 - 摘要：P(AN/IA) copolymers were obtained in a mixture solution of tetramethylene sulfone (TMS)/water and other four different polymerization mediums and polymer conversion rate, weight average molecular weight (Mw) and molecular weight distribution (D), surface micro-topography, monomer reactivity ratios, chain structure, thermal property and spinning performance were investigated.The results showed that with an increase of H2O in the mixed solvent mixture, the polymer conversions were increased firstly and then decreased.The experimental results showed that there were good linear relationships between the weight average molecular weight (Mw) and the ratio of H2O/TMS as well as the other four different polymerization mediums.But Mw and D(less than 2) of P(AN/IA) polymer obtained in H2O/TMS mixture reached the maximum and the minimum, respectively, compared with the other polymerization systems.AN copolymerized with IA in H2O/TMS mixture tended to ideal polymerization, according to statistical predication, the distributing probability of 2IA segment was only 2.83%.Looser structure, smaller particle size, more soluble, lower heat release rate, wider heat release range, smaller reaction energy barrier were required by thermal stabilized ladder-like structure during cyclization reaction of PAN copolymer which could be obtained in H2O/TMS mixture.The apparent viscosity of spinning dope was lower and TMS was an excellent solvent for PAN.关键词：Acrylontirle;Itaconic acid;Mixed solvent;Thermal stability;Spinnability
- 33
- |
- 13
- |
- 0
发布时间：2021-03-19 - 摘要：Well-defined AbBA triblock bottlebrushes with the poly(N, N'-dimethyl acrylamide) (PAm) as A block and polyacrylate densely grafted with polystyrene (PS) as B block were prepared by the combination of controlled radical polymerization and copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction.The composition and structure of the bottlebrushes were confirmed by hydrogen nuclear magnetic resonance (1H-NMR) and gel permeation chromatograph (GPC), which showed a high side-chain grafting density of about 100%.The self-assembly behavior of the bottlebrushes with different PAm contents was investigated under various conditions.The morphologies of assemblies were observed using transmission electron microscope (TEM).Under the identical condition, the amphiphilic bottlebrushes with higher PAm content (>5%) self-assembled into sphere micelles, while the bottlebrushes with lower PAm content trended to form lamellar micelles and vesicles.The effects of initial concentration and solvents were investigated using PAm195-b-(PA-g-PS67)153-PAm195 under different conditions.The increase of the initial concentration changed the micelles from spheres to lamellae/vesicles.A common solvent with the solubility parameter closer to PS increased the mobility of the PS chains in the core, and led to assemblies of vesicles (thermodynamics steady state); while a selective solvent with the solubility parameter differed greatly from PS led to aggregation to form larger vesicles.关键词：Amphiphilic;Cylindrical molecular bottlebrush;Morphologies transformation;Self-assembly;Vesicles
- 73
- |
- 24
- |
- 5
发布时间：2021-03-19 - 摘要：Acrylic acid (AAc) and 2-acrylamide-2-methylpropanesulfonic acid (AMPS) were successfully grafted on polyterafluoroethylene (PTFE) powder by the fact that γ-ray radiation induced graft coploymerization for preparation of high hydrophilic PTFE powder.The chemical structure and hydrophilicity of the grafted PTFE powder were characterized by Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle (CA)test.The surface morphology of the grafted PTFE powder was observed through scanning electron microscope (SEM).The electric potential of the grafted PTFE powder dispersion was determined by zeta potential test.The thermal stability of the grafted PTFE powder was analyzed by thermogravimetric analysis (TGA).It was found that the hydrophilicity and dispersion stability of modified PTFE powder was significantly improved with increasing grafting yield of AAc and AMPS.The PTFE powder with a grafting yield of 26.6% can be stably dispersed in water for a long period, which was prepared in the solution with the monomer concerntration of 20% and the AAc/AMPS ratio of 2 at 70℃.Water contact angle of the PTFE powder decreased from 148.8° before grafting to 30.2° after grafting.Simultaneously, the corresponding zeta potential of PTFE dispersion decreased from-4.3 mV to-83.4 mV.关键词：PTFE;Acrylic acid;2-Acrylamide-2-methylpropanesulfonic acid;Hydrophilic;Pre-irradiation grafting
- 61
- |
- 19
- |
- 4
发布时间：2021-03-19 - 摘要：The phosphorus-containing poly(arylene ether ketone) (P-PAEK) with the advantage of insolubility in BMI resin at the injection temperature was chosen as the toughener of RTM resin.The U3160 carbon fiber reinforced BMI resin composites interlaminar toughened by P-PAEK particles was fabricated via RTM process.Through research on the influence of P-PAEK particles with different contents on the impact strength properties of BMI resin, it was found that the toughness of matrix resin could be greatly improved by adding a few thermoplastic resin particles.The impact strength was increased from 10.3 kJ/m2 to 30.3 kJ/m2.The microscopic morphology was observed by SEM and toughening mechanism was analyzed.When the content of P-PAEK increased, the microstructure of TP/TS system experienced sea-island, co-continuous and phase inversion transition.The sea-island structure could absorb more energy than the other one, which attributed to the toughening mechanism of rigid particles.The interlaminar fracture properties of the composite were characterized by Mode Ⅰ and Mode Ⅱ fracture toughness tests.It was found that the GⅠC and GⅡC of toughened U3160/BMI composites were well improved when the areal density of P-PAEK particles was 2 g/m2.It was improved 56% of GⅠC and 42% of GⅡC compared to the U3160/BMI composites.The mechanical properties of composites were well kept, as the CAI increased by 29% and interlaminar shear strength was 111.7 MPa.关键词：P-PAEK;BMI;Toughened;Composites
- 53
- |
- 16
- |
- 6
发布时间：2021-03-19 - 摘要：Effect of electrostatic interactions between these ions and the charged monomer of polyelectrolyte on the chain conformation and the rheological behavior is a fundamentally important issue for engineering application of polyelectrolyte/ILs systems.Rheological behavior of a polyelectrolyte, sodium polystyrene sulfonate (NaPSS), in 1-allyl-3-methylimidazolium chloride (AmimCl) has been investigated and compared to that in AmimCl/H2O co-solvent solutions.Mole of chain segment unit per liter (mol/L) is used to define the concentration of NaPSS.The results show that, NaPSS in AmimCl solution shows different rheological behaviors from which in salt-free aqueous solution, added salt aqueous solution and neutral polymer in ionic liquid solution.Rheological behaviors of NaPSS in AmimCl/H2O co-solvent solutions are also different from each other.With increasing AmimCl concentration, intrinsic viscosity[η] of NaPSS in AmimCl/H2O decreases, indicating the decline of chain coil size of NaPSS.NaPSS in AmimCl/H2O co-solvent show the rheological behaviors changing from salt-free polyelectrolyte solution to neutral polymer in θ solvent with increasing AmimCl concentration.When the solvent changes into pure AmimCl, NaPSS in AmimCl solution is divided into two concentration regimes in the range from 0.007 mol/L to 0.8 mol/L.Dynamic frequency sweep shows that NaPSS chain does not overlap in the concentration regime bellow 0.29 mol/L, where the power laws for the concentration dependence of specific viscosity and terminal relaxation time are ηsp~cp1.4 and τ~cp0, respectively, similar to theoretical prediction for salt-free polyelectrolyte solutions in entangled regime.The concentration regime above 0.29 mol/L is considered as semidilute un-entangled regime, where the power laws for the concentration dependence of specific viscosity and terminal relaxation time are ηsp~cp3.5 and τ~cp1.9, respectively, closing to theoretical prediction for neutral polymer in good solvents in entangled regime.The unique phenomenon may be caused by the high electrostatic coupling of monomer-ion and monomer-monomer.关键词：Polyelectrolyte;Ionic Liquids (ILs);Electrostatic interaction;Rheological behaviors
- 40
- |
- 22
- |
- 0
发布时间：2021-03-19 - 摘要：Bisphenol-fluorene polycarbonate (BHPF-PC) was synthesized by melt transesterification of 9, 9-bis(4-hydroxyphenyl) fluorene (BHPF) and disphenyl carbonate(DPC).The chemical structure of the polymer was confirmed by a combination of FTIR, 1H-NMR and 13C-NMR spectra tests.The influences of catalyst species and contents, the initial DPC/BHPF molar ratios, polymerization time and temperature on the chemophysical properties of BHPF-PC were investigated.Two kinds of quaternary phosphonium salts including tetraphenylphosphonium phenolate (C30H25OP) and three kinds of inorganic salts were used as catalysts for the polymerization preparation of BHPF-PC, among which C30H25OP showed the highest catalytic activity.The impact of the initial DPC/BHPF molar ratios on the molecular weight of BHPF-PC was analyzed based on GPC measurements, and it was found that the molecular weight increased sharply when DPC was used in slight excess and then decreased with further increase of DPC/BHPF molar ratio.Furthermore, the effect of preparing conditions, such as polymerization time and temperature on the molecular weight variation of BHPF-PC was evaluated.The result indicated that the reaction time for obtaining maximum molecular weight increases with increasing initial molar ratio of DPC to BHPF.The BHPF-PC prepared by the condensation of DPC and BHPF with molar ratio of 1.1:1 in the presence of 1×10-5 mol/mol of C30H25OP, a residence time of 150 minutes at 330℃, showed a desirably high molecular weight.Finally, the thermal and optical properties of BHPF-PC were evaluated.BHPF-PC has a glass transition temperature of 275℃, an initial decomposition temperature of 440℃ (T5%), and a light transmittance of 88.1%, indicating that BHPF-PC is an optical transparent material having excellent resistance to high temperature.关键词：9, 9-Bis(4-hydroxyphenyl) fluorene;Polycarbonate;Melt transesterification;Tetraphenyl-phosphonium phenolate
- 62
- |
- 23
- |
- 3
发布时间：2021-03-19
Research Article
- Postal code：100190
- Tel：010-62588927 Email：gfzxb@iccas.ac.cn
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备05002797号-8
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0